# 练习1：在屏幕上显示跑马灯文字。

import os
from time import sleep
if __name__ == '__main__':
    content = '我是跑马灯'
    length = len(content)
    while True:
        for i in range(0, length):
            print(' '*i + content[i])
            sleep(0.3)
            os.system('cls')
            